After today, you will be able to… Define the term polarity Explain why certain atoms have more pull on electrons Identify molecules as either polar or non-polar based off of its symmetry Identify which geometries will generally be polar molecules

Unit 4: Chemical Bonding Polar and Non-Polar Molecules Day 4 - Notes

Polarity Polar bond: Bonds where the electrons are shared unequally between atoms –The atom that is more electronegative will pull the electrons closer to itself –When atoms are different, each has a different pull on the electrons.

The shared electrons are held closer to fluorine, because it is more electronegative. H F Example: HF -δ-δ +δ+δ Polar Molecule Example

Non-polar bond: Electrons are shared equally between two atoms. –Atoms that are the same have the same pull on the shared electrons (same E.N. value)

Example: H 2 Example: CCl 4 HH Both atoms have the same E.N. value. Non-Polar Molecule Examples All atoms surrounding carbon are the same, therefore all electrons are shared equally. C Cl

General rules: 1.Different atoms around a central atom will always be polar molecules. 2.Same atoms around a central atom are always non-polar molecules. How do you know if a molecule is polar or non-polar?

Examples: Polar vs. Non-Polar Non-polar H 2 versusHF Polar HH H F

Examples: Polar vs. Non-Polar Non-polar CO 2 versusCOS Polar OC O SC O

Examples: Polar Molecules Polar H 2 ONH 3 Polar O H H N H H H Picture the unshared electrons as a different atom! BENT and PYRAMID will always be polar.

Examples: Polar vs. Non-Polar Non-Polar CH 4 CH 3 Cl Polar C H H H H C H H H Cl

Examples: Polar Molecule Polar CH 2 O C O H H Although exceptions exist, for this class, PLANAR will always be polar.